Effects of propranolol on myocardial oxygen consumption, substrate extraction, and haemodynamics in hypertrophic obstructive cardiomyopathy

Long-term follow-up study on obstructive hypertrophic cardiomyopathy patients treated with disopyramide: evidences of a notable trend in symptom control within a real-world clinical setting

Background

In obstructive hypertrophic cardiomyopathy (HOCM), disopyramide is used in patients who remain symptomatic despite β-blockers or verapamil. However, effectiveness of disopyramide therapy has not been clearly established due to inconsistent definition of responders and the insufficient length of follow-ups reported in literature. To address these shortcomings, we have conducted a retrospective analysis from detailed databases with long follow-up, from two HCM Referral Centers.

Methods

62 symptomatic HOCM patients (43% women, age 52 ± 14 years) with left ventricular (LV) outflow tract gradient (LVOTG) ≥ 50 mmHg at rest or during provocation, were recruited from two Italian Centers. Disopyramide was added as second-line therapy in the patients in whom symptoms persisted despite classic pharmacologic treatment. Patients in NYHA class > II at baseline who reached NYHA class II or I, and patients in NYHA class II at baseline who reached NYHA class I or symptoms stabilization were defined as responders.

Results

At follow-up, (mean 4.4 years, IQR 1.1-6.6 years), 47 patients (76%) were responders, whereas 15 (24%) were no-responders. Responders showed larger LV diastolic volume index (LVEDVi) at baseline as compared to no-responders (61 ± 14 vs. 49 ± 16 ml, respectively, p = 0.018), and, at follow-up, reached lower LVOTG than no-responders (43 ± 32 vs. 66 ± 28 mmHg, respectively, p = 0.013), with a LVOTG <50 mmHg more represented in responders than in no-responders (75% vs. 25%, respectively; p = 0.004). No side effects requiring discontinuation of the therapy were recorded.

Conclusion

HOCM patients treated with disopyramide as second-line therapy in a quite long-follow-up showed a significant improvement of symptoms, which avoided SRT in up to 70% of them. Moreover, our data suggest that a larger LVEDVi at baseline identify the subgroup of patients who benefit the most from the therapy in terms of symptoms and reduction of LVOTG below 50 mmHg during treatment. We will discuss specific situations where disopyramide may be preferred over myosin inhibition to ensure that effective therapeutic options are fully considered and not prematurely dismissed.

Obstructive hypertrophic cardiomyopathy: a review of new therapies

Hypertrophic cardiomyopathy (HCM) is a phenotypically heterogeneous disease with a genetic basis and variable penetrance. The hallmarks of HCM include dynamic left ventricular outflow tract obstruction, typically caused by asymmetric septal hypertrophy. However, abnormal papillary muscle placement, abnormal mitral valve and subvalvular apparatus and apical hypertrophic forms have also been described. Typical medical treatment has been stagnant for decades, although there have been significant advances in surgical treatment of patients with obstructive HCM. Herein, we describe a new class of drugs targeting the specific pathophysiology of HCM.

Effects of Metoprolol on Exercise Hemodynamics in Patients With Obstructive Hypertrophic Cardiomyopathy

BACKGROUND

The relationship between exercise hemodynamics, loading conditions, and medical treatment in patients with obstructive hypertrophic cardiomyopathy (HCM) is incompletely understood.

OBJECTIVES

This study aimed to investigate the effect of metoprolol on invasive hemodynamic parameters at rest and during exercise in patients with obstructive HCM.

METHODS

This randomized, double-blind, placebo-controlled crossover trial enrolled 28 patients with obstructive HCM and New York Heart Association functional class ≥II. Patients were randomized to initiate either metoprolol 150 mg or placebo for 2 consecutive 2-week periods. Right-heart catheterization and echocardiography were performed at rest and during exercise at the end of each treatment period. The primary outcome was the difference in pulmonary capillary wedge pressure (ΔPCWP) between peak exercise and rest.

RESULTS

No treatment effect on ΔPCWP was observed between metoprolol and placebo treatment (21 ± 9 mm Hg vs 23 ± 9 mm Hg; P = 0.12). At rest, metoprolol lowered heart rate (P < 0.0001), left ventricular outflow tract (LVOT) gradient (P = 0.01), and increased left ventricular end-diastolic volume (P = 0.02) and stroke volume (SV) (+6.4; 95% CI: 0.02-17.7; P = 0.049). During peak exercise, metoprolol was associated with a lower heart rate (P < 0.0001), a lower LVOT gradient (P = 0.0005), lesser degree of mitral regurgitation (P = 0.004), and increased SV (+9 mL; 95% CI: 2-15 mL; P = 0.008).

CONCLUSIONS

In patients with obstructive HCM, exercise was associated with an abnormal rise in PCWP, which was unaffected by metoprolol. However, metoprolol increased SV at rest and peak exercise following changes in end-diastolic volume, LVOT gradient, and degree of mitral regurgitation. (The Effect of Metoprolol in Patients With Hypertrophic Obstructive Cardiomyopathy [TEMPO]; NCT03532802).

Management of Hypertrophic Cardiomyopathy in a Newborn with Dextro-Transposition of the Great Arteries

Impaired maternal glucose metabolism during pregnancy can have significant effects on the cardiovascular system of the developing fetus. Early in pregnancy the teratogenic effects may lead to structural heart defects, while later in gestation a form of hypertrophic cardiomyopathy can develop due to overgrowth driven by fetal hyperinsulinism. We describe an infant with the uncommon combination of both dextro-transposition of the great arteries and hypertrophic cardiomyopathy. We emphasize the importance of a longitudinal multi-disciplinary approach, from fetal diagnosis to post-operative management, that allowed for an excellent outcome in this rare combination of severe cardiac malformations.

Hypertrophic Cardiomyopathy and Atrial Fibrillation: A Review

Hypertrophic cardiomyopathy (HCM) is an inherited cardiological condition that exhibits various clinical symptoms. The leading cause of atrial fibrillation (AF) in patients with HCM is advanced diastolic dysfunction and left atrial dilatation and remodeling. In addition to the gradual symptomatic and functional decline caused by AF, there is an increased risk of thromboembolic disease and mortality, especially if there is a rapid ventricular rate or obstruction of the left ventricular outflow tract. The mainstay of management of AF in HCM is a combination of non-pharmacological lifestyle and risk factor modification, long-term anticoagulation, and rhythm control with anti-arrhythmic medications, septal ablation, and radiofrequency catheter ablation. This article has examined the development of AF in HCM, its clinical symptomatology, and its impact, highlighting its management and the mortality associated with AF in HCM.

Pharmacotherapy for the treatment of obstructive hypertrophic cardiomyopathy

Introduction: Hypertrophic cardiomyopathy (HCM) is one of the most common genetic heart diseases and represents a leading cause of sudden cardiac death as well as a prevalent cause of heart failure and stroke. HCM is characterized by a very complex pathophysiology, consisting of heterogeneous clinical manifestations and natural history. Left ventricular outflow tract (LVOT) obstruction has been considered the most knowable feature of HCM since the initial clinical descriptions of the disease.Areas covered: In this review, the authors discuss the most recent reports on the pharmacological treatment of obstructive HCM, mainly based on three different levels of intervention: control of symptoms, cardiac metabolism modulation and disease-modifying approaches, including genetic preventive therapies.Expert opinion: There are presently limited data supporting pharmacological interventions for this complex disease. However, an improved understanding of HCM pathophysiology will allow the development of novel treatment options. Two important key messages are to further study drugs with negative but limited previous results and to design new and larger trials for those molecules that have already produced positive results in HCM, especially for pressure gradients and symptoms control.

Myocardial Efficiency: A Fundamental Physiological Concept on the Verge of Clinical Impact

Myocardial external efficiency is the relation of mechanical energy generated by the left (or right) ventricle to the consumed chemical energy from aerobic metabolism. Efficiency can be calculated invasively, and, more importantly, noninvasively by using positron emission tomography, providing a single parameter by which to judge the adequacy of myocardial metabolism to generated mechanical output. This parameter has been found to be impaired in heart failure of myocardial or valvular etiology, and it changes in a characteristic manner with medical or interventional cardiac therapy. The authors discuss the concept, strengths, and limitations, known applications, and future perspectives of the use of myocardial efficiency.

Anti-arrhythmic therapy in patients with non-ischemic cardiomyopathy

Implantable cardiac defibrillators (ICD) are the foundation of therapy for the prevention of sudden cardiac death. While ICDs prevent SCD, they do not prevent the occurrence of ventricular arrhythmias which are usually symptomatic. Though catheter ablation has been successful in substrate modification of ventricular tachycardia in patients with ischemic cardiomyopathy, there is much less evidence to support its use in non-ischemic cardiomyopathy. Therefore, anti-arrhythmic drugs (AADs) are an essential adjunctive therapy for secondary prevention of ventricular arrhythmias in patients with non-ischemic cardiomyopathy. In patients with hypertrophic cardiomyopathy (HCM) and dilated cardiomyopathy (DCM), the prevalence of ventricular arrhythmias correlates with the volume of scar as characterized by late gadolinium enhancement. Beta-blockers forms the cornerstone of treatment to prevent ventricular arrhythmias in both HCM and DCM. Disopyramide is an important therapeutic option in HCM as it provides both negative inotropy which reduces obstruction as well as lass I anti-arrhythmic action. In DCM sotalol, through is combined beta-blocking and class III AD effects, significantly reduces the burden of ventricular arrhythmias. Though amiodarone is efficacious in the prevention of ventricular arrhythmias in both HCM and DCM, its use is limited by its side-effects profile. Evidence for AAD therapy for arrhythmogenic right ventricular dysplasia (ARVD) is limited by its low prevalence and lack of studies. ICDs have been shown to reduce SCD regardless of whether patients are receiving AAD therapy.

Hypertrophic cardiomyopathy: a review

Hypertrophic cardiomyopathy (HCM) is a global disease with cases reported in all continents, affecting people of both genders and of various racial and ethnic origins. Widely accepted as a monogenic disease caused by a mutation in 1 of 13 or more sarcomeric genes, HCM can present catastrophically with sudden cardiac death (SCD) or ventricular arrhythmias or insidiously with symptoms of heart failure. Given the velocity of progress in both the fields of heart failure and HCM, we present a review of the approach to patients with HCM, with particular attention to those with HCM and the clinical syndrome of heart failure.

Shortening baroreflex delay in hypertrophic cardiomyopathy patients -- an unknown effect of β-blockers

AIMS

Hypertrophic cardiomyopathy (HCM) is characterized by left ventricular hypertrophy and impaired diastolic and systolic function. Abnormal sympathetic-parasympathetic balance is a potential stimulus for left ventricular hypertrophy in HCM patients. β-Blockers are routinely used in HCM for their strong negative inotropic effect; however, these drugs also influence the sympathetic-parasympathetic balance. This study aimed to determine the autonomic control of the cardiovascular system and the autonomic effects of β-blockers in HCM patients treated or untreated with β-blockers.

METHODS

Among 51 HCM outpatients (18-70 years old; 29 men) there were 19 individuals with no medication and 32 subjects treated with a β-blocker. Fourteen age- and gender-matched (23-70 years old; nine men) healthy volunteers were enrolled in the control group. Continuous, non-invasive finger blood pressure was recorded during supine rest for 30 min. Autonomic regulation of the cardiovascular system was measured by heart rate variability and spontaneous baroreflex function (cross-correlation sequence method).

RESULTS

The mean pulse interval, time domain and spectral measures of heart rate variability and baroreflex sensitivity were comparable between HCM patients, treated or not with β-blockers, and the control group. However, the delay of the baroreflex was significantly longer in HCM patients who were not treated with β-blockers [2.0 (1.6-2.3) s] in comparison with HCM patients receiving β-blockers [1.4 (1.1-1.8) s; P = 0.0072] or control subjects [1.2 (0.8-1.8) s; P = 0.0025]. This delay did not differ between HCM patients treated with β-blockers and the control group.

CONCLUSIONS

Hypertrophic cardiomyopathy not treated with β-blockers is accompanied by prolonged baroreflex delay. The use of β-blockers normalizes this delay.

Pharmacological treatment options for hypertrophic cardiomyopathy: high time for evidence

Hypertrophic cardiomyopathy (HCM) is the most common genetic heart disease, affecting over one million individuals in Europe. Hypertrophic cardiomyopathy patients often require pharmacological intervention for control of symptoms, dynamic left ventricular outflow obstruction, supraventricular and ventricular arrhythmias, and microvascular ischaemia. Current treatment strategies in HCM are predicated on the empirical use of long-standing drugs, such as beta-adrenergic and calcium blockers, although with little evidence supporting their clinical benefit in this disease. In the six decades since the original description of the disease, <50 pharmacological studies enrolling little over 2000 HCM patients have been performed, the majority of which were small, non-randomized cohorts. As our understanding of the genetic basis and pathophysiology of HCM improves, the availability of transgenic and preclinical models uncovers clues to novel and promising treatment modalities. Furthermore, the number of patients identified and followed at international referral centres has grown steadily over the decades. As a result, the opportunity now exists to implement adequately designed pharmacological trials in HCM, using established as well as novel drug therapies, to potentially intervene on the complex pathophysiology of the disease and alter its natural course. Therefore, it is timely to review the available evidence for pharmacological therapy of HCM patients, highlight the most relevant gaps in knowledge, and address some of the most promising areas for future pharmacological research, in an effort to move HCM into the era of evidence-based management.

Pacing for drug-refractory or drug-intolerant hypertrophic cardiomyopathy

BACKGROUND

Hypertrophic cardiomyopathy (HCM) is a genetic disease with an autosomal-dominant inheritance for which negative inotropes are the most widely used initial therapies. Observational studies and small randomised trials have suggested symptomatic and functional benefits using pacing and several theories have been put forward to explain why. Pacing, although not the primary treatment for HCM, could be beneficial to patients with relative or absolute contraindications to surgery or alcohol ablation. Several randomised controlled trials comparing pacing to other therapeutic modalities have been conducted but no Cochrane-style systematic review has been done.

OBJECTIVES

To assess the effects of pacing in drug-refractory or drug-intolerant hypertrophic cardiomyopathy patients.

SEARCH METHODS

We searched the following on the 14/4/2010: CENTRAL (The Cochrane Library 2010, Issue 1), MEDLINE OVID (from 1950 onwards ), EMBASE OVID (from 1980 onwards ), Web of Science with Conference Proceedings (from 1970 onwards). No language restrictions were applied.

SELECTION CRITERIA

Randomised controlled trials of either parallel or crossover design that assess the beneficial and harmful effects of pacing for hypertrophic cardiomyopathy were included. When crossover studies were identified, we considered data only from the first phase.

DATA COLLECTION AND ANALYSIS

Data from included studies were extracted onto a pre-formed data extraction paper by two authors independently. Data was then entered into Review Manager 5.1 for analysis. Risk of bias was assessed using the guidance provided in the Cochrane Handbook. For dichotomous data, relative risk was calculated; and for continuous data, the mean differences were calculated. Where appropriate data were available, meta-analysis was performed. Where meta-analysis was not possible, a narrative synthesis was written. A QUROUM flow chart was provided to show the flow of papers.

MAIN RESULTS

Five studies (reported in 10 papers) were identified. However, three of the five studies provided un-usable data. Thus the data from only two studies (reported in seven papers) with 105 participants were included for this review. There was insufficient data to compare results on all-cause mortality, cost effectiveness, exercise capacity, Quality of life and Peak O2 consumption.When comparing active pacing versus placebo pacing on exercise capacity, one study showed that exercise time decreased from (13.1 ± 4.4) minutes to (12.6 ± 4.3) minutes in the placebo group and increased from (12.1 ± 5.6) minutes to (12.9 ± 4.2) minutes in the treatment group (MD 0.30; 95% CI -1.54 to 2.14). Statistically significant data from the same study showed that left ventricular outflow tract obstruction decreased from (71 ± 32) mm Hg to (52 ± 34) mm Hg in the placebo group and from (70 ± 24) mm Hg to (33 ± 27) mm Hg in the active pacing group (MD -19.00; 95% CI -32.29 to -5.71). This study was also able to show that New York Heart Association (NYHA) functional class decreased from (2.5 ± 0.5) to (2.2 ± 0.6) in the inactive pacing group and decreased from (2.6 ± 0.5) to (1.7 ± 0.7) in the placebo group (MD -0.50; 95% CI -0.78 to -0.22).When comparing active pacing versus trancoronary ablation of septal hypertrophy (TASH), data from one study showed that NYHA functional class decreased from (3.2 ± 0.7) to (1.5 ± 0.5) in the TASH group and decreased from (3.0 ± 0.1) to (1.9 ± 0.6) in the pacemaker group. This study also showed that LV wall thickness remained unchanged in the active pacing group compared to reduction from (22 ± 4) mm to (17 ± 3) mm in the TASH group (MD 0.60; 95% CI -5.65 to 6.85) and that LV outflow tract obstruction decreased from (80 ± 35.5) mm Hg in the TASH group to (49.3 ± 37.7) mm Hg in the pacemaker group.

AUTHORS' CONCLUSIONS

Trials published to date lack information on clinically relevant end-points. Existing data is derived from small trials at high risk of bias, which concentrate on physiological measures. Their results are inconclusive. Further large and high quality trials with more appropriate outcomes are warranted.

Relation of coronary microvascular dysfunction in hypertrophic cardiomyopathy to contractile dysfunction independent from myocardial injury

We studied the spatial relations among hyperemic myocardial blood flow (hMBF), contractile function, and morphologic tissue alterations in 19 patients with hypertrophic cardiomyopathy (HC). All patients were studied with oxygen-15 water positron emission tomography during rest and adenosine administration to assess myocardial perfusion. Cardiovascular magnetic resonance was performed to derive delayed contrast-enhanced images and to calculate contractile function (E(cc)) with tissue tagging. Eleven healthy subjects underwent similar positron emission tomographic and cardiovascular magnetic resonance scanning protocols and served as a control group. In the HC group, hMBF averaged 2.46 ± 0.91 ml/min/g and mean E(cc) was -14.7 ± 3.4%, which were decreased compared to the control group (3.97 ± 1.48 ml/min/g and -17.7 ± 3.2%, respectively, p <0.001 for the 2 comparisons). Delayed contrast enhancement (DCE) was present only in patients with HC, averaging 6.2 ± 10.3% of left ventricular mass. In the HC group, E(cc) and DCE in the septum (-13.7 ± 3.6% and 10.2 ± 13.6%) significantly differed from the lateral wall (-16.0 ± 2.8% and 2.4 ± 5.9%, p <0.001 for the 2 comparisons). In general, hMBF and E(cc) were decreased in segments displaying DCE compared to nonenhanced segments (p <0.001 for the comparisons). In the HC group, univariate analysis revealed relations of hMBF to E(cc) (r = -0.45, p <0.001) and DCE (r = -0.31, p <0.001). Multivariate analysis revealed that E(cc) was independently related to hMBF (beta -0.37, p <0.001) and DCE (beta 0.28, p <0.001). In conclusion, in HC hMBF is impaired and related to contractile function independent from presence of DCE. When present, DCE reflected a progressed disease state as characterized by an increased perfusion deficit and contractile dysfunction.

The diagnosis and treatment of hypertrophic cardiomyopathy

BACKGROUND

Hypertrophic cardiomyopathy (HCM) is the most common hereditary disease of the heart.

METHODS

In this article, we summarize the current state of the diagnosis and treatment of HCM on the basis of a selective review of recent publications with relevance to clinical practice.

RESULTS

Several hundred mutations in more than 27 genes, most of which encode sarcomeric structures, are associated with the HCM phenotype. Thus, HCM can be thought of as a sarcomeric disease, with myocardial fiber disarray as its histological hallmark. There are two types of HCM, a more common, obstructive type (HOCM, 70%) and a less common, non-obstructive type (HNCM; in all cases of HCM, testing should be performed to detect outflow obstruction at rest and/or on provocation, and to thereby determine whether HOCM or HNCM is present. The symptoms of HCM include dyspnea, angina pectoris, palpitations, dizziness, and occasionally syncope. Because sudden cardiac death is the most serious complication of HCM, particularly in young and asymptomatic patients, it follows that correct diagnosis, followed by risk stratification of patients with regard to the need for prophylactic implantation of an implantable cardiac defibrillator (ICD), can be of life-saving importance. The pharmacotherapy of symptomatic HNCM consists of the treatment of heart failure with a normal ejection fraction (HFNEF). In HOCM, the patient's symptoms and the obstructive gradient are the guide to treatment with beta-blockers or verapamil. For patients with drug-resistant disease, surgical myectomy and percutaneous septal ablation are now standard treatments.

CONCLUSION

A near-normal life expectancy and a highly satisfactory quality of life are now realistic treatment goals for patients with HCM.

Comparison of acute reduction in left ventricular outflow tract pressure gradient in obstructive hypertrophic cardiomyopathy by disopyramide versus pilsicainide versus cibenzoline

Negative inotropic agents are often administered to decrease the left ventricular (LV) pressure gradient in patients with obstructive hypertrophic cardiomyopathy (HC). Little information is available regarding comparisons of the effects on LV pressure gradient among negative inotropic agents. The present study compared the decrease in the LV pressure gradient at rest in patients with obstructive HC after treatment with pilsicainide versus treatment with disopyramide or cibenzoline. The LV pressure gradient and LV function were assessed before and after the intravenous administration of each drug. In 12 patients (group A, mean pressure gradient 90 ± 24 mm Hg), the effects of disopyramide, propranolol, and verapamil were compared. In another 12 patients (group B, mean pressure gradient 98 ± 34 mm Hg), a comparison was performed among disopyramide, cibenzoline, and pilsicainide. In group A, the percentage of reduction in the LV pressure gradient was 7.7 ± 9.9% with verapamil, 19.0 ± 20.2% with propranolol, and 58.6 ± 15.0% with disopyramide, suggesting that disopyramide was more effective than either verapamil or propranolol. In group B, the percentage of reduction in the LV pressure gradient was 55.3 ± 26.6% with disopyramide, 55.3 ± 20.6% with cibenzoline, and 54.7 ± 15.4% with pilsicainide, suggesting an equivalent effect on the LV pressure gradient for these 3 agents. In conclusion, these results indicate that the acute efficacy for the reduction of the LV pressure gradient at rest by pilsicainide (a pure sodium channel blocker) was equivalent to that of disopyramide or cibenzoline (combined sodium and calcium channel blockers). Accordingly, sodium channel blockade might be more important for reducing the LV pressure gradient at rest in patients with obstructive HC than calcium channel blockade or β blockade.

Determinants of myocardial energetics and efficiency in symptomatic hypertrophic cardiomyopathy

PURPOSE

Next to hypertrophy, hypertrophic cardiomyopathy (HCM) is characterized by alterations in myocardial energetics. A small number of studies have shown that myocardial external efficiency (MEE), defined by external work (EW) in relation to myocardial oxidative metabolism (MVO(2)), is reduced. The present study was conducted to identify determinants of MEE in patients with HCM by use of dynamic positron emission tomography (PET) and cardiovascular magnetic resonance imaging (CMR).

METHODS

Twenty patients with HCM (12 men, mean age: 55.2 + or - 13.9 years) and 11 healthy controls (7 men, mean age: 48.1 + or - 10 years) were studied with [(11)C]acetate PET to assess MVO(2). CMR was performed to determine left ventricular (LV) volumes and mass (LVM). Univariate and multivariate analyses were employed to determine independent predictors of myocardial efficiency.

RESULTS

Between study groups, MVO(2) (controls: 0.12 + or - 0.04 ml x min(-1) x g(-1), HCM: 0.13 + or - 0.05 ml x min(-1) x g(-1), p = 0.64) and EW (controls: 9,139 + or - 2,484 mmHg x ml, HCM: 9,368 + or - 2,907 mmHg x ml, p = 0.83) were comparable, whereas LVM was significantly higher (controls: 99 + or - 21 g, HCM: 200 + or - 76 g, p < 0.001) and MEE was decreased in HCM patients (controls: 35 + or - 8%, HCM: 21 + or - 10%, p < 0.001). MEE was related to stroke volume (SV), LV outflow tract gradient, NH(2)-terminal pro-brain natriuretic peptide (NT-proBNP) and serum free fatty acid levels (all p < 0.05). Multivariate analysis revealed that SV (ss = 0.74, p < 0.001) and LVM (ss = -0.43, p = 0.013) were independently related to MEE.

CONCLUSION

HCM is characterized by unaltered MVO(2), impaired EW generation per gram of myocardial tissue and subsequent deteriorated myocardial efficiency. Mechanical external efficiency could independently be predicted by SV and LVM.

Heart failure with preserved ejection fraction in older adults

Age-associated physiologic changes predispose older adults to develop heart failure, even when left ventricular ejection fraction is normal or near normal. Heart failure with a preserved ejection fraction is particularly common in older hypertensive women, and hypertension plays a key role in its pathophysiology. In contrast with heart failure with a reduced ejection fraction, the treatment of heart failure with a preserved ejection fraction has a limited empiric basis, although some basic principles are useful. Ongoing studies provide hope of improving care of these patients.

The value of changes in QRS width and in ST-T segment during exercise test in hypertrophic cardiomyopathy for identification of associated coronary artery disease

OBJECTIVES

Non-invasive methods cannot reliably predict the presence of coronary artery disease (CAD) in hypertrophic cardiomyopathy (HCM). This study aims to define the accuracy of QRS width changes versus standard ST-T criteria for recognition of associated ischemic CAD in patients with HCM undergoing exercise testing (ET).

METHODS

A retrospective study including patients with HCM. HCM was defined by left ventricular hypertrophy (LVH) of unknown etiology of at least 15 mm. Coronary angiography was performed as a gold standard for definition of CAD (> or =70% obstruction in at least one major artery). QRS width duration was measured at peak ET by a computerized method employing an optical scanner. No changes in QRS width or shortening during ET were considered normal; QRS width prolongation of more than 3 ms was defined as abnormal.

RESULTS

68 patients (56/12 M/F) aged 60+/-12 y were studied. During ET, abnormal QRS response was found in 40 (58.8%) and Ischemic ST-T changes in 52 (76.5%) patients. CAD in at least one artery was diagnosed in 31 patients (45.5%). The sensitivity of QRS width versus ST-T changes during ET for associated CAD was 82% and 28%, respectively. Specificity was 75% and 48%, respectively. Positive and negative predictive values were 88%; 68% for QRS width and 67%; 59% for ST-T changes respectively.

CONCLUSIONS

In patients with HCM undergoing ET, the association with CAD was more accurately predicted by an increase in QRS complex width than by standard criteria of ST-T segment changes. Thus, its use should be encouraged, especially in patients with HCM.

Alcohol septal ablation for obstructive hypertrophic cardiomyopathy

Treatment of obstructive hypertrophic cardiomyopathy remains challenging. Medical therapy, surgical therapy, and pacemaker therapy have been shown to be beneficial in some patients over the years. Alcohol septal ablation is a catheter-based intervention that causes a controlled infarct in the septum leading to a decrease in the left ventricular outflow tract obstruction. Along with the impressive reductions in left ventricular outflow tract gradient, there is subjective and objective improvement in symptoms. Development of complete heart block requiring a permanent pacemaker after alcohol septal ablation remains a frequent complication, but has decreased in some recent studies. Alcohol septal ablation has been shown to improve diastolic function, decrease mitral regurgitation, decrease left ventricular hypertrophy and mass, as well as cause changes at the cellular and molecular level that improve myocardial function. Comparison of alcohol septal ablation to surgical myectomy has shown favorable results. Long-term follow-up of alcohol septal ablation has shown sustained results out to several years.

Role of controlled septal infarct in hypertrophic obstructive cardiomyopathy

Hypertrophic obstructive cardiomyopathy is a complex and challenging disease. Medical therapy, surgical therapy, and pacing therapy have been used with some success over the years. Nonsurgical septal reduction therapy, also called alcohol septal ablation, has been used recently as a percutaneous catheter-based intervention to improve left ventricular outflow tract obstruction and thereby improve symptoms. The reported results of this procedure have shown impressive reductions in gradient and improvement in symptoms at relatively low risk. The most common complication of the procedure, development of complete heart block requiring a permanent pacemaker, has improved in recent studies with refinements of the procedural technique. Nonsurgical septal reduction therapy has been shown to improve diastolic function, decrease left ventricular hypertrophy and mass, and cause changes at the cellular and molecular level that improve myocardial function. Reported results at 1 year follow-up continue to show benefit, and long-term studies are ongoing.

[Therapeutic approaches in symptomatic hypertrophic obstructive cardiomyopathy]

Hypertrophic cardiomyopathy is a complex and heterogeneous disease. Although most patients experience just a few symptoms, and have a good prognosis, there are others whose symptoms are severe and progressive, determined by different pathophysiological elements such as diastolic dysfunction, myocardial ischemia, arrhythmias and subaortic obstruction. Approximately 20-30% of hypertrophic cardiomyopathy patients develop an intraventricular dynamic gradient, which in some cases, is responsible for severe symptoms which are ameliorated once the obstruction is reduced. In many cases the symptoms can be controlled with medical treatment which includes betablockers, calcium-channel antagonists and dysopiramide, but some patients will still experience severe and refractory symptoms. This subgroup of patients, which represent approximately 5-10% of patients with hypertrophic cardiomyopathy, can be problematic from a management perspective. For many years, septal myectomy and/or mitral valve replacement offered the only effective alternative therapy for these patients. However, the high rates of morbidity and mortality associated with these procedures have necessitated the search for new and less invasive procedures such as ventricular pacing and percutaneous septal ablation. Although the initial results with sequential pacing were encouraging, further studies have suggested a significant placebo effect, which makes its application controversial. In the last 5 years selective embolization of the septal artery precipitating a localized myocardial infarction has been utilized to reduce the subaortic gradient. The potential indications and efficacy of these new forms of treatment, like ventricular pacing and percutaneous septal ablation, are presently under evaluation and are the main subject of this review. Medical treatment, with either beta-blockers, calcium channel antagonists or dysopiramide constitutes the first therapeutic step. Surgery, while alleviating the subaortic obstruction and reducing the intraventicular pressure and mitral insufficiency, produces important and long-lasting symptomatic and functional improvement in most of these patients, and it continues to be an important therapeutic alternative in these cases. If the first results with sequential pacemaker implants were encouraging, today it is alluded to an important placebo effect that causes its application to be controversial. In the last 5 years the path has been made in the creation of a septal infarction located through the embolization of the septal branches to reduce the gradient.

Noninvasive indexes of left atrial diastolic function in hypertrophic cardiomyopathy

OBJECTIVES

Our goal was to noninvasively assess left atrial diastolic function and its relation to the impaired left ventricular filling in patients with hypertrophic cardiomyopathy.

METHODS AND RESULTS

We studied 34 patients with hypertrophic cardiomyopathy, 26 patients with secondary forms of left ventricular hypertrophy (aortic stenosis, fixed subaortic stenosis, hypertension), and 21 control subjects. Left atrial diastolic function was assessed by measuring acceleration time (SAT), deceleration time (SDT), and the EF (mean deceleration rate) slope of the pulmonary venous flow systolic wave (SW). Left ventricular diastolic function assessed by transmitral Doppler included peak early left ventricular and peak atrial filling velocities, the ratio of early-to-late peak velocities, isovolumic relaxation time, deceleration time, and EF slope. In patients with hypertrophic cardiomyopathy, acceleration time was significantly reduced (P<.05), deceleration time was significantly prolonged (P<.0001), and EF slope was significantly reduced (P<.01). These indexes were similar among the other two groups. No statistically significant difference existed between the subgroups of hypertrophic cardiomyopathy in the above indexes. Patients with hypertrophic cardiomyopathy and secondary forms of left ventricular hypertrophy had evidence of left ventricular diastolic dysfunction. In patients with hypertrophic cardiomyopathy, no correlation existed between left atrial and left ventricular diastolic function indexes (r = -0.26 to 0.33).

CONCLUSIONS

Echocardiographic indexes of left atrial relaxation and filling are abnormal in patients with hypertrophic cardiomyopathy but not in secondary forms of left ventricular hypertrophy. These indexes are abnormal in all forms of hypertrophic cardiomyopathy irrespective of left ventricular outflow tract obstruction and distribution of hypertrophy; they are not solely attributable to left ventricular diastolic dysfunction. The above may imply that hypertrophic cardiomyopathy is a cardiac myopathic disease that involves the heart muscle as a whole, irrespective of distribution of hypertrophy and obstruction.

An equation to predict the changes in peak left ventricular pressure in hypertrophic obstructive cardiomyopathy after treatment: application to the administration of disopyramide

A theoretical equation was derived based on the time-varying elastance model to predict theoretically the relationship between the delay in the onset of left ventricular outflow obstruction and the reduction in peak left ventricular pressure (LVP) caused by treatment in hypertrophic obstructive cardiomyopathy (HOCM). ECG, LVP, and other hemodynamic parameters were measured during catheterization at a constant heart rate with atrial pacing in 16 patients with HOCM before and after intravenous administration of disopyramide (1 mg/kg). After disopyramide administration, the duration between the R wave of the ECG and the onset of obstruction (T1) was prolonged significantly (from 117 +/- 30 to 155 +/- 32 ms, P < 0.0001), and peak LVP was reduced significantly (from 222 +/- 42 to 177 +/- 39 mmHg, P < 0.0001). The relation between the prolongation of T1 and the percent reduction in peak LVP was predicted well by the theoretical equation (coefficient of determination R2 = 0.926). Our model simplifies the therapeutic strategy for reducing the left ventricular outflow pressure gradient in patients with HOCM, which is to delay the time of onset of obstruction by some methods.

Effects of diltiazem on myocardial perfusion abnormalities during exercise in patients with hypertrophic cardiomyopathy

The effect of diltiazem on myocardial ischemia in patients with hypertrophic cardiomyopathy (HCM) was evaluated by exercise myocardial 201Tl single photon emission computed tomography (SPECT). Exercise myocardial SPECT was performed before and 8 weeks after oral administration of diltiazem (180 mg/day) in 20 patients with HCM who showed transient perfusion defects on exercise myocardial 201Tl SPECT under control conditions. SPECT images were divided into 17 segments. The 201Tl perfusion defects were visually scored and evaluated as the defect score. The transient dilation index was calculated as an index of subendocardial ischemia. Improvement of the defect score was demonstrated in 15 patients after the administration of diltiazem. The mean defect score decreased significantly from 9.90 +/- 5.17 to 5.50 +/- 4.89 (p < 0.0001). Although 16 of 20 patients showed an abnormal transient dilation index before diltiazem treatment, 16 showed improvement and 13 of these normalized after diltiazem therapy. The mean transient dilation index decreased from 1.16 +/- 0.10 to 1.02 +/- 0.09 (p < 0.0001). In conclusion, diltiazem prevents or diminishes myocardial ischemia in patients with HCM.

Reverse redistribution of Tc-99m-tetrofosmin in exercise myocardial SPECT in patients with hypertrophic cardiomyopathy

We examined the usefulness of Tc-99m-tetrofosmin in detecting exercise induced perfusion abnormalities in patients with hypertrophic cardiomyopathy (HCM) and to clarify time-related changes in myocardial distribution of Tc-99m-tetrofosmin after a single injection. We studied 44 consecutive patients with HCM by means of exercise/rest Tc-99m-tetrofosmin single photon emission computed tomography (SPECT). After injecting 370 MBq of Tc-99m-tetrofosmin at the peak exercise, the early SPECT imaging was performed at 30 min (EX-30) and the delayed imaging at 180 min (EX- 180). Immediately after the delayed imaging, 740 MBq of Tc-99m-tetrofosmin was injected in the resting state, and the rest SPECT imaging was performed 30 min later. Exercise-induced regional perfusion defects and/or apparent reversible left ventricular cavity dilation were identified in 26 (68.2%) of the 44 patients. When EX-30 images and EX-180 images were compared, reverse redistribution was confirmed in 36 patients (81.8%). Reverse redistribution was detected most frequently in the septal portion of the anterior wall, followed by the septal portion of the posterior wall and the septum. Exercise/rest Tc-99m-tetrofosmin myocardial imaging was a useful method for assessing myocardial perfusion abnormalities in patients with HCM. Reverse redistribution was detected very frequently on early and delayed images of exercise. We assumed that reverse redistribution may reflect a retention disorder of Tc-99m-tetrofosmin caused by some metabolic dysfunction of myocytes.

Myocardial ischemia detected by thallium scintigraphy is frequently related to cardiac arrest and syncope in young patients with hypertrophic cardiomyopathy

OBJECTIVES

The purpose of this study was to determine the frequency of myocardial ischemia as a potential mechanism for cardiac arrest and syncope in young patients with hypertrophic cardiomyopathy who experienced such complications.

BACKGROUND

Sudden cardiac death and syncope occur frequently in patients with hypertrophic cardiomyopathy. Although ventricular arrhythmias account for most of these events in adult patients, the mechanism responsible for cardiac arrest and syncope in young patients has not been established.

METHODS

Twenty-three patients with hypertrophic cardiomyopathy, aged 6 to 23 years, with previous cardiac arrest (n = 8), syncope (n = 7) or a family history of sudden cardiac death (n = 8) were evaluated to determine the prevalence of spontaneous ambulatory ventricular tachycardia (24- to 72-h electrocardiographic [ECG] monitoring), exercise-induced myocardial ischemia (thallium scintigraphy) and inducibility of ventricular tachycardia (electrophysiologic studies).

RESULTS

Three of 15 patients with a history of cardiac arrest or syncope had ventricular tachycardia on ambulatory ECG monitoring. However, all 15 patients, had inducible ischemia by thallium scintigraphy compared with only 3 (37%) of 8 patients with no such history (p < 0.01). In contrast, ventricular tachycardia induction was uncommon in all of the young patients (27% in those with cardiac arrest or syncope; 0% in the others). During therapy for ischemia with verapamil alone or in combination with beta-adrenergic blocking agents, only 4 of the 15 patients with cardiac arrest or syncope had further episodes. In three of the four patients, these events were temporally related to discontinuation of verapamil. Among eight patients who had a repeat exercise thallium study while receiving anti-ischemic therapy, seven (88%) had improved regional thallium uptake, of whom three had normal thallium studies.

CONCLUSIONS

These data suggest that in young patients with hypertrophic cardiomyopathy, sudden cardiac arrest or syncope is frequently related to ischemia rather than to a primary arrhythmogenic ventricular substrate.

Long-term course and cardiac sympathetic nerve activity in patients with hypertrophic cardiomyopathy

OBJECTIVE

To investigate the relation between regional myocardial sympathetic nerve activity and the electrocardiographic and cardiac functional changes in hypertrophic cardiomyopathy.

DESIGN

A retrospective study to compare the findings of myocardial scintigraphy with iodine-123 metaiodobenzylguanidine (MIBG) and the serial electrocardiographic changes.

SETTING

Myocardial scintigraphy was performed with iodine-123 MIBG and thallium-201 and single photon emission computed tomography (SPECT) in the division of nuclear medicine of Kanazawa University Hospital. Both SPECT studies were performed within a week.

PATIENTS

22 patients with hypertrophic cardiomyopathy classified according to their serial electrocardiographic changes--namely, 15 patients with an increase in or the appearance of a negative T wave (group A) and seven patients with a conduction disturbance or a decrease in or disappearance of the negative T wave (group B). The mean follow up period was 45 (range 12-143) months.

RESULTS

Group B showed a high rate of decreased activity or defects in MIBG uptake compared with group A (p less than 0.005). The areas of decreased activity or defects corresponded with the hypertrophied portion of the left ventricular wall. Although the early myocardial uptake (MIBG: thallium ratio) was similar in both groups, the mean (SD) MIBG clearance rate was significantly higher (p less than 0.05) in group B (0.25 (0.17)) than in group A (0.10 (0.15)).

CONCLUSION

Abnormalities of regional myocardial sympathetic nerve activity may be important in patients with hypertrophic cardiomyopathy and suspected progression of myocardial damage.

Evidence for or against efficacy of beta-blockers and aspirin for management of feline cardiomyopathies

Feline myocardial diseases today are largely represented by disorders involving LV hypertrophy. They may be attended by arrhythmias, congestive heart failure, systemic hypertension, thromboembolic complications, and sudden death. These structural myocardial disorders and their hemodynamic and electrocardiographic derangements may cause or result in variable degrees of diastolic dysfunction. Propranolol and aspirin represent two agents commonly employed to treat feline cardiomyopathies for more than 15 years. Nevertheless, clinical data describing their effect on morbidity and mortality are lacking. It is likely that propranolol administered at moderate to high doses effects favorable responses in some cats with clinical signs attributable to severe hypertrophy, outflow obstruction, or tachyarrhythmias. It is unknown whether clinical improvements are due to direct myocardial effects or (more likely) secondary responses to a beta-adrenergic blockade reduction in heart rate or contractility. Personal experience also indicates that high numbers of cats have received the drug for many years in combination with other therapies (especially furosemide) and remain in a compensated state of heart failure without untoward drug effects. On the other hand, many cardiomyopathic cats experience heart failure, arrhythmias, and death despite treatment with beta-blocking agents. Feline thromboembolism is a devastating complication of cardiomyopathic disorders. Until or unless the primary cause(s) of current diseases is elucidated to promote disease reversal, factors responsible for thrombus formation will accompany the heart diseases, protected from effective management. It appears unlikely that aspirin as currently recommended produces any obvious benefit in treating or preventing thromboembolism. Modifications of therapeutic protocols prescribing these frequently used drugs await well-constructed clinical trials evaluating their efficacy with respect to cardiovascular morbidity and mortality.

Hypertrophic cardiomyopathy: prognosis with medical or surgical therapy

Over the past 30 years, knowledge of the natural history and effects of therapy in patients with hypertrophic cardiomyopathy has expanded greatly, but progress has been hampered by its variable patterns of expression. Many but not all patients show symptomatic improvement with medical treatment. Chronic beta blockage does not appear to affect long-term survival, whereas results with calcium channel blockade by verapamil have been encouraging; however, they await confirmation, and verapamil may be hazardous in some patients with severe left ventricular (LV) outflow tract obstruction and elevated LV end-diastolic pressure. Reported beneficial effects of amiodarone on survival also require further study. Surgical therapy has become the treatment of choice for medically refractory patients with proven outflow tract obstruction. In several centers, the operative risk is low, and long-term follow-up demonstrates prolonged symptomatic relief. It is hoped that work currently underway will provide more definitive information on the long-term effects of the role of calcium channel blockers, antiarrhythmic medications, and the long-term effects of surgical therapy on survival of patients with this disorder.

Decreased coronary vasodilatory capacity in hypertrophic cardiomyopathy determined by split-dose thallium-dipyridamole myocardial scintigraphy

Split-dose thallium-dipyridamole myocardial scintigraphy was performed in patients with nonobstructive hypertrophic cardiomyopathy (HC) who had angiographically normal coronary arteries. The dipyridamole-induced increases in thallium-201 uptake, calculated to evaluate coronary vasodilatory capacity, were significantly lower in 30 patients with HC than in 13 control subjects (177 +/- 58 vs 281 +/- 46%) and the reductions were observed in both the septal and lateral segments. The reductions of the septal segment in HC patients were significantly greater than those in 10 hypertensive patients with comparable degrees of septal hypertrophy. Of patients with HC, 16 had increases in thallium uptake well below the normal range. Compared with those having normal increases, these patients had significantly lower exercise duration (11 vs 15 minutes), with 33% having ST depression develop at a workload less than or equal to 80 watts. These data indicate that approximately one-half of patients with HC have impaired coronary vasodilatory capacity that could be an important pathophysiologic abnormality of HC resulting in the development of myocardial ischemia and the impairment of cardiac performance during exercise.

Relation between extent of left ventricular hypertrophy and diastolic filling abnormalities in hypertrophic cardiomyopathy

In hypertrophic cardiomyopathy, the relation between left ventricular diastolic impairment and magnitude of left ventricular hypertrophy has not been clearly defined. In the present study, Doppler echocardiographic indexes of left ventricular diastolic filling were compared in 78 patients with hypertrophic cardiomyopathy and in 72 normal control subjects of similar age, and the relation between abnormalities of diastolic filling and magnitude of left ventricular hypertrophy was assessed. In patients with hypertrophic cardiomyopathy, isovolumic relaxation was prolonged (94 +/- 25 ms); peak early diastolic flow velocity (53 +/- 18 cm/s), deceleration of flow velocity in early diastole (341 +/- 142 cm/s2) and the ratio between early and late peaks of flow velocity (1.6 +/- 0.9) were reduced; and peak late diastolic flow velocity was increased (38 +/- 15 cm/s) compared with values in control subjects (76 +/- 12 ms, 65 +/- 12 cm/s, 512 +/- 131 cm/s2, 2.3 +/- 0.8 and 30 +/- 7 cm/s, respectively; p less than 0.001). Individual patient analysis showed that diastolic filling was abnormal in 52 (67%) of the 78 patients with hypertrophic cardiomyopathy. However, within the patient group, none of the Doppler diastolic indexes showed a significant correlation with maximal left ventricular wall thickness or the wall thickness index (correlation coefficients ranged from -0.15 to 0.10).(ABSTRACT TRUNCATED AT 250 WORDS)

Myocardial stunning in hypertrophic cardiomyopathy: recovery predicted by single photon emission computed tomographic thallium-201 scintigraphy

A young woman with hypertrophic cardiomyopathy confirmed by echocardiography and cardiac catheterization presented with chest pain and features of a large left ventricular aneurysm. The initial diagnosis was myocardial ischemia with either an evolving or an ancient myocardial infarction. Subsequently, verapamil therapy was associated with complete resolution of the extensive left ventricular wall motion abnormalities, normalization of left ventricular ejection fraction and a minimal myocardial infarction. Normal thallium uptake on single photon emission computed tomographic scintigraphy early in the hospital course predicted myocardial viability in the region of the aneurysm. Thus, orally administered verapamil may reverse spontaneous extensive myocardial ischemia in hypertrophic cardiomyopathy and possibly limit the extent of myocardial infarction in such circumstances.

Verapamil prevents silent myocardial perfusion abnormalities during exercise in asymptomatic patients with hypertrophic cardiomyopathy

Recent studies indicate that reversible 201Tl perfusion defects, compatible with silent myocardial ischemia, commonly develop during exercise in asymptomatic or mildly symptomatic patients with hypertrophic cardiomyopathy (HCM). To determine whether this represents a dynamic process that may be modified favorably by medical therapy, we studied 29 asymptomatic or minimally symptomatic patients with HCM, aged 12-55 years (mean, 28), with exercise 201Tl emission computed tomography under control conditions and again after 1 week of oral verapamil (mean dosage, 453 mg/day). Treadmill time increased slightly during verapamil (21.0 +/- 3.6 to 21.9 +/- 2.7 minutes, p less than 0.005), but peak heart rate-blood pressure product was unchanged (26.3 +/- 6.0 X 10(3) compared with 25.0 +/- 6.4 X 10(3). Two midventricular short-axis images per study were divided into five regions each, and each of these 10 regions was then analyzed on a 0-2 scale by three observers blinded with regard to the patients' therapy. Average regional scores of 1.5 or less were considered to represent perfusion defects, and a change in regional score of 0.5 or more was considered to constitute a significant change. During control studies, 15 patients (52%) developed perfusion defects with exercise (average, 3.7 regions per patient). In 14 of these patients, all perfusion defects completely reversed after 3 hours of rest; one patient had fixed defects. After administration of verapamil, exercise perfusion scores improved in 10 of the 14 patients (71%) with reversible defects; there was overall improvement in 34 of 50 (68%) regions with initially reversible perfusion defects.(ABSTRACT TRUNCATED AT 250 WORDS)

Long-term outcome of patients with hypertrophic cardiomyopathy successfully resuscitated after cardiac arrest

This study describes the long-term outcome of 33 patients with hypertrophic cardiomyopathy who experienced a cardiac arrest but were successfully resuscitated. Cardiac arrest occurred at ages 9 to 62 years (mean 32); five patients survived multiple (two or three) arrests. A variety of treatments were administered; 18 patients with left ventricular outflow tract obstruction underwent ventricular septal myotomy-myectomy or mitral valve replacement and also received drug therapy; 15 patients received medical therapy alone. To date, 22 (67%) of the 33 patients have survived after the initial cardiac arrest for periods of 17 months to 22 years (mean 7 years); 12 patients have survived for greater than or equal to 5 and 6 for greater than or equal to 10 years. Of the 22 survivors, 16 have remained asymptomatic or only mildly symptomatic over the period of follow-up; 6 others have become severely symptomatic with heart failure, including 3 with evidence of left ventricular wall thinning and cavity enlargement. Eight patients ultimately died of natural cardiac causes (suddenly or of progressive heart failure) 7 months to 8.4 years (mean 4 years) after their initial cardiac arrest. Actuarial patient survival was 97 +/- 3%, 74 +/- 9% and 61 +/- 11% after 1, 5 and 10 years, respectively. Event-free rate (defined as actuarial survival without recurrent cardiac arrest of death) was 83 +/- 7%, 65 +/- 9% and 53 +/- 11%, respectively. For this group of patients with hypertrophic cardiomyopathy who were treated in a nonsystematic fashion with a variety of therapeutic strategies, the long-term outcome after surviving a cardiac arrest was variable.(ABSTRACT TRUNCATED AT 250 WORDS)

Regional myocardial blood flow and metabolism at rest in mildly symptomatic patients with hypertrophic cardiomyopathy

Previous observations and clinical manifestations suggest the presence of ischemia in the disproportionately thickened septum of patients with hypertrophic cardiomyopathy. Metabolic consequences of ischemia can be demonstrated with positron emission tomography. Therefore, 10 patients with hypertrophic cardiomyopathy and an echocardiographic septum to posterior wall thickness ratio of 1.8 +/- 0.4 cm (range 1.3 to 2.5) were studied with the use of nitrogen (N)-13 ammonia, carbon (C)-11 palmitate and fluoro (F)-18 2-deoxyglucose as tracers of myocardial blood flow, fatty acid metabolism and exogenous glucose utilization. The results of positron emission tomography in 9 patients with hypertrophic cardiomyopathy were compared with those in 10 normal volunteers. In the hypertrophic cardiomyopathy group, observed myocardial activity of N-13 ammonia and C-11 palmitate in the septum was similar to that in the lateral wall. Septum to lateral wall tissue activity ratios averaged 1.04 +/- 0.15 for N-13 ammonia and 1.04 +/- 0.18 for C-11 palmitate, and were similar to those in the normal volunteers (0.98 +/- 0.07 and 0.98 +/- 0.03, respectively; p = NS). Myocardial clearance half-time and residual fraction of C-11 palmitate did not differ significantly between the septum and lateral wall. However, F-18 2-deoxyglucose uptake was significantly lower in the septum than in the lateral wall (15,768 +/- 4,314 versus 19,818 +/- 5,234 counts/pixel; p less than 0.003). The mean septum to lateral wall activity ratio of 0.83 +/- 0.21 was less than that observed in normal volunteers (0.92 +/- 0.07; p = NS).(ABSTRACT TRUNCATED AT 250 WORDS)

Beta-adrenergic stimulation with isoproterenol enhances left ventricular diastolic performance in hypertrophic cardiomyopathy despite potentiation of myocardial ischemia. Comparison to rapid atrial pacing

Impaired left ventricular relaxation and filling is an important pathophysiologic mechanism in hypertrophic cardiomyopathy. To determine whether isoproterenol, known to improve relaxation in isolated cardiac muscle, could favorably modify this effect, we assessed simultaneous left ventricular volume and regional systolic asynchrony (by radionuclide angiography), left ventricular pressure (by micromanometer catheters), and lactate metabolism in 12 patients with hypertrophic cardiomyopathy. Pressure-volume relations were studied during atrial pacing stress to induce myocardial ischemia and during isoproterenol infusion to similar heart rates. Angina occurred in 10 patients with pacing and in 11 patients during isoproterenol infusion; lactate consumption was reduced in nine patients during isoproterenol compared with pacing, including five patients who produced lactate with isoproterenol. During isoproterenol compared with pacing, peak left ventricular pressure was higher (205 +/- 33 vs. 142 +/- 21 mm Hg, p less than 0.001), ejection fraction was higher (77 +/- 10% vs. 71 +/- 12%, p less than 0.02), and regional systolic nonuniformity was diminished. Despite ischemia, these changes in load and nonuniformity during isoproterenol were associated with enhanced diastolic function compared with pacing tachycardia: isoproterenol reduced T 1/2, the half-time of pressure decline after peak negative dP/dt (from 46 +/- 10 to 33 +/- 6 msec, p less than 0.001), shifted the diastolic pressure-volume curve downward and rightward in 10 of 12 patients, and increased end-diastolic volume (from 77 +/- 18% to 100 +/- 11% of control values, p less than 0.001) with no change in end-diastolic pressure (19 +/- 7 to 19 +/- 5 mm Hg, p = NS). Thus, despite ischemia, isoproterenol improved left ventricular relaxation and filling compared with tachycardia in the absence of beta-adrenergic stimulation. Although isoproterenol is detrimental in hypertrophic cardiomyopathy by provoking ischemia, these data suggest that the adverse effects of ischemia on ventricular relaxation and distensibility may be alleviated by beta-adrenergic stimulation, possibly as a result of enhanced inactivation and restored load sensitivity.